An important consideration for regulating passage of solar energy through a device is in the optical property of a surface of the device facing the sunlight. In devices which are to be utilized to absorb solar energy, extraordinary large proportions of solar energy flow determined by the solar constants may be harnessed as useful energy where the surface facing the sun utilizes layers which absorb the energy over the frequency range of the sunlight while reflecting little or only a small amount of energy in the long-wave infra-red region. In a vacuum the proportion of incidence to reflected radiation determines the amount of useable energy derived from the sunlight. In solar heaters as used in conventional installations which are not in a vacuum, an important perameter is the convection current of ambient air contacting the device. When the air is still, roofs on which the devices are installed may reach temperatures of 100.degree. or more which creates considerable convection currents. The convection currents also exist under low wind velocity conditions whereby the device is deprived of absorbing a substantial portion of the solar energy to which it is subjected. At higher wind velocity conditions, the use of such a device becomes questionable. The detrimental effects of the convection currents also apply in situations where the device is used to emit the energy and reflect solar energy and whereby heat is given off to the ambient air.
Prior art devices, for example as shown in U.S. Pat. No. 3,072,920, have proposed use of optically active layers which face the sun and are separated from ambient air by an air space. The air space in such devices however is of such size and dimension that convection currents within the space may occur thus decreasing the amount of solar energy which may be absorbed when the device is used as a sun collector or decreasing the amount of energy which may be radiated when the device is used to radiate heat to ambient air. It is therefore a purpose of my invention to provide for a solar conditioning device of simplified construction which may readily absorb solar energy or radiate thermal energy and which includes means to prevent convection flow of air over an optically active surface facing the sun.